The present invention relates to an unloading device for filter press.
It is known that filter presses are used to filter liquid substances; said filter presses are constituted in practice by a series of plates which are recessed in a central region and are arranged in a pack; respective elements made of filtering cloth are interposed between said plates, so as to form a succession of chambers into which the liquid to be filtered is fed. The plates and the associated cloths have corresponding holes forming, upon assembly, a duct which is used to feed the liquid to be filtered; in order to prevent the cloths from clinging to the plates, during filtration, said plates are provided with respective grooves which also facilitate the flow of the filtrate toward the lower part, wherefrom the flow is drawn by means of appropriate channels.
The pack of plates is pressed between a fixed head and a movable head by means of a suitable jack which acts axially with respect to said pack. For this purpose, the plates are slidably supported on opposite lateral guides arranged horizontally parallel to each other and appropriately rigidly coupled to the fixed head.
In a widespread embodiment, a single filtering cloth is folded on the upper edge of each plate so as to descend on the opposite sides thereof and cover its respective front surfaces. The fabric is furthermore tightly fitted to the plate by appropriate laces which are tied at the sides of said plate. Sometimes, however, there are two separate cloths which are applied on the opposite surfaces of each plate and are rigidly coupled to one another by lateral laces. The filtering cloths can furthermore be suspended from an upper support by appropriate elastic means ensuring the appropriate tension.
Filtering cloths are also known which are formed by two distinct elements which are mutually coupled by a collar intended to enter said hole of the plate. Said cloths are obviously perforated at said collar.
The solid residue filtered from the liquid is collected in the above mentioned chambers defined between the adjacent plates, until it forms a sort of brick or cake. Said brick is in contact with respective filtering cloths on its opposite surfaces.
It therefore becomes necessary to periodically unload from the filter press the bricks formed by the filtration residues. This operation is generally performed by mutually spacing the plates, by virtue of the sliding of the movable head, so as to open the filtration chambers and allow the falling out of said bricks due to gravity.
Sometimes, however, the bricks do not separate, due to the force of adhesion to the filtering cloths, thus requiring the intervention of an operator who manually performs an appropriate mechanical action. This obviously entails a significant limitation to the productivity of the filter press.
Furthermore, in order to allow manual intervention for cleaning it is necessary to provide a wide opening of the chambers, i.e. a considerable mutual spacing of the plates. This leads to a correspondingly large bulk of the filter press and to the need to use an expensive opening jack.
In order to obviate this problem, various unloading devices have been provided which are intended, for example, to impart a reciprocating motion to the bricks in order to facilitate their separation. However, these devices are generally complicated and do not ensure complete separation of the bricks.